I actually found this place whilst looking for help... which is probably not an ideal way to start a user review for my new One, but more of that in a second.
I've come from a Galaxy Nexus and it's taken me a few hours to get used to the HTC Sense stuff again (had a Desire many moons ago). Overall it's a nice layout, although I do wish you could remove Blinkfeed if you didn't want to use it. Never mind.
In terms of build, screen and sound quality it's light years ahead of the Nexus and by far the most impressive phone I've ever owned. Nice weight to it, good shape... the audio almost blew my ears off when I decided to experiment with how loud it'd be through headphones at max volume... yeah, overall it's a lovely bit of kit.
Camera is pretty tidy too. I'd say it's not quite up to the standard of the Xperia Z (which my other half has), but it's certainly not far from it.
But (and you all knew that was coming)... thing is, I'm having the dreaded HTC GPS problems that - a bit of checking has revealed - seems to have plagued them for a few years. Initially I wasn't too concerned that the device couldn't find my location for the clock and weather application, but as time went on and Google Maps started struggling to lock onto anything I started feeling a bit iffy. Going online and finding the amount of issues previous HTC handsets seem to have had with this has only deepened my fear the the One still has a serious issue that HTC haven't been able to eradicate from their last gen of handsets.
To do a simple test, I strolled outside and sat my old Nexus alongside the One and fired up Google Maps. The Nexus homed in on my location in three seconds. After 8 minutes of searching, Maps on the One failed to find my location at all.
At the moment all I can really do is sit it out for a day or two and see if it magically rights itself. Such a shame, as everything else the phone does it does with a flourish.